The concentration of water treatment agents in industrial water systems is traditionally controlled based on intermittent measurements of the concentration of the water treatment agent(s) in the water of the system and/or the concentration of the specie or condition targeted by the water treatment agent (the target specie). The measurements of the concentration of the water treatment agent(s) in the water of the system, and any responsive in-system concentration adjustments, are commonly based only on occasional grab samples, taken for instance once or twice per shift (a shift commonly encompassing about 8 to 12 hours of system operating time) or once every several days.
Traditional methods of determining the concentration of a water treatment agent in a water system are usually somewhat cumbrous and/or protracted, and/or provide results that are merely estimates and/or variable (for instance, dependent upon a person's laboratory technique). Long time delays typically exist between changes in system operation and a compensating change in treatment dosage. Analyses for water treatment agents have heretofore generally been made using classical (wet chemistry) techniques, at times accompanied by water flowmeter and/or conductivity readings. A sample of water from the system is taken and a wet chemical test is performed. The conventional wet chemical tests include titrations or manual addition of reagents to the water sample that react with the species of interest to form a turbid or colored solution that can be measured with an optical spectrophotometer. The turbidity or intensity of the color is proportional to the concentration of the species of interest. For example, phosphate concentrations are determined by a spectrophotometric (colorimetric) test. Concentrations of pyrophosphate and organic phosphorus compounds are determined using the same spectrophotometric test after a digestion (reversion) step.
Many of the conventional analytical methods for measuring the concentration of water treatment agents are susceptible to interference from other materials in the water sample, in some instances methods are nonexistent, and/or are subjective, such as visual observation of color change. For instance, colorimetric analysis of orthophosphate is a commonly used technique, but it is susceptible to turbidity interference.
The more accurate a conventional manual (grab sample) analysis technique, the more protracted that technique can be. Feedback information can at times even be days behind the sampling and hence of little value in providing data from which a dosage-regulation response can be determined. Moreover, the concentration of the water treatment agent may well have changed during the elapsed interval.
Estimating the in-system concentration for a water treatment agent, and in turn regulating the feed of the treatment agent to meet a target in-system concentration, is further complicated by other imprecise evaluations of operating parameters. The rate at which the water treatment agent is being fed to the industrial water system, and/or other operating parameters having an influence on the in-system concentration of the water treatment, may defy precise or accurate measurement. The readings and/or settings on feed equipment and/or lines are seldom unquestionably reliable. Fluctuations in the concentration of the water treatment agent may stem from a variety of system conditions, such as dilution when other materials are charged to the system, concentration by evaporation, steam generation or other means, unaccounted loss of fluid from the system, and the like, some of which parameters may not be accurately known.
Even when accurate indications of the mass or volume of a water treatment agent feed delivered to a system are available, and accurate water treatment agent residual concentrations are available, if the residual concentration determinations are based on grab or intermittent samples, any extrapolation therefrom to a value for the system consumption of the water treatment agent is based on fragmentary data and outdated information. A change in the in-system concentration might not be detected until it has had a significant impact on treatment agent and system performance. The regulation of in-system concentration will be at least in part a response after the active agent's performance has changed. When the detection of system consumption change is delayed, the responsive regulation of a treatment agent's in-system concentration will invariably be late and system performance may suffer. When the responsive regulation of in-system concentration is late, underfeeding or overfeeding of the treatment agent routinely will occur to some extent between the time the system's consumption for the water treatment agent changed and the time the treatment agent in-system concentration is adjusted and/or system operating parameter (e.g., alkalinity) adjustment.
In an industrial water system plant the use of any estimated, variable, intermittent, fragmentary or historic data (for instance data from a method that inherently has a long response delay time or is non-selective, such as conductivity analysis) severely diminishes the sensitivity of any concentration-fluctuation responsive regulation of the water treatment agent feed rate and/or diminishes the ability to follow changes in the in-system concentration with appropriate compensations to the water treatment agent feed rate.
Conventional procedures for regulating water treatment agent in-system concentration are further complicated by other imprecise evaluations of operating parameters. The rates at which the water treatment agent is being fed to and/or removed from the industrial water system and/or other operating parameters having an influence on the in-system concentration of the water treatment, may defy precise measurement unless inert tracers and selective analytical methods are used. The readings and/or settings on feed and blowdown equipment and/or lines are seldom unquestionably reliable and often complicated by multiple sources of blowdown and makeup and changes in composition of those water samples. Fluctuations in the concentrations in the target species and the water treatment agent may stem from a variety of system conditions, such as dilution when other materials are charged to the system, concentration by evaporation or other means, unaccounted loss of fluid from the system and the like, some of which parameters may not be accurately known. Generally all sources of water intake and loss, and all sources of water treatment agent intake and loss, cannot be known precisely and continuously unless inert tracers and selective analytical methods are used.
A sensitive, selective, and rapid concentration-fluctuation responsive control of water treatment agent in-system concentration would render most any industrial water system more efficient. A sensitive and rapid consumption responsive control of water treatment agent in-system concentration would render most any industrial water system more efficient. Overfeeding of a water treatment agent is unnecessarily expensive, may at times diminish the recycling potential of waste water discharged from the system, and may also at times impair system performance. Underfeeding of a water treatment agent almost inevitably impairs system performance, the imbalance between an underfed water treatment agent and its target species leading to higher degrees of deleterious effect(s) from which relief is sought by the water treatment. In some water systems an imbalance between the concentrations of water treatment agents charged to the system and the system's water conditions and/or target species can severely diminish the efficiency of the system. For instance, an imbalance in water treatment agent concentration can diminish the efficiency of a temperature conditioning performance (such as heat exchange) or a heat transfer performance (such as steam generation), or diminish the performance of a process to which a water system is adjuvant.
It is an object of the present invention to provide a method or process for regulating the in-system concentration of one or more water treatment agents to a water system that can be conducted on-site in a very short time period. It is an object of the present invention to provide a method or system for regulating the in-system concentration of a water treatment agent in an industrial water system that is concentration-fluctuation responsive and can be conducted on-site, preferably on a continuous basis. It is an object of the present invention to provide a method or system for regulating the in-system concentration of a water treatment agent in an industrial water system that is system consumption responsive and can be conducted on-site, preferably on a continuous basis. It is an object of the present invention to provide in an industrial water system one or more monitorings of in-system concentration for water treatment agents on-site in a very short time period, preferably on a continuous basis. It is an object of the present invention to provide in an industrial water system at least one monitoring of an in-system concentration for a water treatment agent in the water system, together with the monitoring of a water treatment agent's system consumption, to provide a sensitive regulation of such in-system concentration on-site in a very short time period, preferably at least in part on a continuous basis. These and other objects of the present invention are described in detail below.